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Generator 81L and 27 protection

Generator 81L and 27 protection

Generator 81L and 27 protection

(OP)
Hi

I have a 1MW diesel generator. How does one prevent the UF (81L) and UV (27) protection functions from operating during startup? I have been told of

a) enough delay to ensure gen has started before protection operates or

b) using poledead logic - these functions are only enabled when the gen cb is closed.

Are there any other methods? What is a typical start up time for this size and type generator?

Thanks in advance.

RE: Generator 81L and 27 protection

Time delay works well. You could also use logic arranged to ignore trips until the relays pull in the first time. I have not heard of option (b) for a stand-alone generator.

If it's starting warm (has a proper jacket heater), time to rated output can be as short as 6 to 8 seconds. Longer times are sometimes used when permissible and wear on the engine is a concern.

RE: Generator 81L and 27 protection

veritas,
modern relays sense the pole dead condition from the voltage input and block (there is no need even to wire the CB status contact for that purpose).

RE: Generator 81L and 27 protection

Hi Veritas.
It's depend on your relay.
1. As Raghun saied, newer relay have internal block for the 27 function, 0.2Un dead zone/block, same for 81<, underfrequncy.
2. If possible add, block from CB position is also help in few cases, for example, open CB with stop command to motor w/o open command to AVR..result, false trip by 27 or 81.
3. Delay. same issue, is depend.
Best Regards.
Slava

RE: Generator 81L and 27 protection

(OP)
Everyone

Thanks for all your valuable contributions. You have ceretainly given me enough to go on with.

Regards.

Veriats.

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